1. Field of the Invention
The present invention relates to an image compensation apparatus by which inputted digital images are compensated to fit characteristics of a display device.
2. Discussion of the Related Art
Generally, digital TV remarkably enhances its image resolution to enable an audience to view images much sharper than those of the previous analog TV. Many developments are made to various high-resolution display devices to represent high-resolution images. And, a large-screen projection TV, PDP TV, projector, and the like stand in the spotlight of display devices of digital TV as well as direct-view type CRT that was previously popular.
Each display device has unique display characteristics. And, Gamma Compensation using three one-dimensional look-up tables, as shown in FIG. 1 is previously used in compensating these characteristics. Such a method is classically known and used worldwide, in which compensation curves are stored for R, G, and B components of an inputted image, respectively to compensate an input-to-output characteristic. Gamma Compensation enables to compensate Gamma characteristic of a display device but is unable to adjust degradation of the color sense caused by various display devices such as CRT, LCD projection TV, PDP, etc. Moreover, Gamma Compensation fails to restore the color sense for an original image prior to photographing via camera.
In order to settle the above problem in FIG. 1, i.e., in order to output the same color of the image photographed via a camera to a display device regardless of various kinds of display devices, a method of storing output RGB values corresponding to input RGB values respectively in a look-up table, as shown in FIG. 2, is proposed. By taking characteristics of a display device into consideration, output values for input combinations for 256-steps R-images, 256-steps G-images, and 256-steps B-images are stored in the look-up table to compensate the characteristics of the display device. In other words, an inputted image is compensated to output using 256×256×256×24-bits look-up table for a predetermined RGB image, whereby an image quality is enhanced or the characteristics of the display device is compensated.
However, such a method is theoretically perfect but has great difficulty in hardware implementation. Namely, about 400 Mbits memory is needed to implement 3-dimensiaonl 256×256×256×24-bits look-up table. Moreover, in ASIC implementation, the look-table itself needs hardware of about a half billion gates, thereby becoming substantially impossible.